Graphene nanoribbons (GNRs) are a single or a few layers of the well-known carbon allotrope graphitic carbon, which possesses exceptional electrical and physical properties which may lead to application in electronic devices, transistor fabrication and oil additives. GNRs structurally have high aspect ratio with length being much longer than the width or thickness.
Graphene nanoplatelets (GNPs) are similar to GNRs except that that the length is in the micron or sub-micron range and hence GNPs lack the high aspect ratio of GNRs. GNPs also possess many of the useful properties of carbon nanotubes (CNTs) and GNRs.
GNRs have been prepared by CVD and from graphite using chemical processes. Most typically GNRs were prepared from CNTs by chemical unzipping and the quality of GNRs depends the purity of the CNT starting material.
GNPs have been typically prepared from graphite by chemical exfoliation, thermal shock and shear, or in a plasma reactor. However, the above methods fail to provide GNRs and GNPs in high yield, good purity with good control of width and length.
Recently, a number of methods have emerged which convert carbon nanotubes to GNRs in good yield and high purity (Hirsch, Angew Chem. Int. Ed. 2009, 48, 2694). More extreme conditions of some of the above methods used to prepare GNRs can result in the synthesis of GNPs from GNRs. However, the purity and uniformity of carbon nanotubes and of the GNRs and GNPs produced from these CNTs is determined by the method of manufacture of the CNTs.
Current CNT manufacturing methods typically produce CNTs which include significant impurities such as, for example, metal catalysts and amorphous carbons. Purification steps are typically required after synthesis of CNTs, which are flow reactor methods to provide carbon nanotubes which are not contaminated with significant amounts of metal catalysts and amorphous carbon. CNT purification steps require large and expensive chemical plants which makes producing large quantities of CNTs of greater than 90% purity extremely costly. Furthermore, present CNT manufacturing methods produce CNTs with low structural uniformity (i.e., CNTs of variable lengths).
Accordingly, what is needed are new methods for providing high quality and inexpensive GNRs and GNPs with high structural uniformity and purity. These methods will involve preparing CNTs of high structural uniformity and purity which then may be converted to GNRs and GNPs of high structural uniformity and purity.